Steady-state twitch Ca2+ fluxes and cytosolic Ca2+ buffering in rabbit ventricular myocytes
Steady-state twitch Ca2+ fluxes and cytosolic Ca2+ buffering in rabbit ventricular myocytes
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DOI：
10.1152/ajpcell.1996.270.1.c192
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发表时间：
1996-01-01
影响因子：
5.5
通讯作者：
Bers, DM
中科院分区：
文献类型：
--
作者：
Delbridge, LMD;Bassani, JWM;Bers, DM
在全细胞电压钳过程中，在吲哚1负载的分离的兔心室肌细胞中测量细胞内Ca 2+（[Ca 2 +]（i））瞬变和跨肌膜Ca 2+电流，以定量胞浆Ca 2+内流的组分，并描述稳态收缩（0.5 Hz，22 ℃）过程中胞浆Ca 2+缓冲的动态方面。根据钳夹期间记录的积分Ca 2+电流（I-Ca）直接测量肌膜Ca 2+内流（158 +/- 10阿托摩尔;阿莫尔）。肌浆网（SR）Ca 2+含量由在快速应用和持续暴露于咖啡因以引起SR Ca 2+负荷（1，208 +/- 170阿莫尔）释放期间诱导的综合生电Na+/Ca 2+交换电流（I-X）确定。平均稳态SR Ca 2+负荷计算为87 +/- 131 μ M（pmol/l非线粒体胞质体积）。通过I-Ca流入的Ca 2+相当于抽搐期间储存的SR Ca 2+的14%和总细胞质Ca 2+通量的23%（47 +/- 6 μ M）。电生理测量的Ca 2+通量与Ca 2+瞬变的比较得出，咖啡因收缩的表观缓冲值为60，抽搐的表观缓冲值为110（总Delta Ca 2 +/无Delta Ca 2+）。这与抽搐期间SR Ca 2+摄取对胞质Ca 2+的“主动"缓冲的发生是一致的。
Intracellular Ca2+ ([Ca2+](i)) transients and transsarcolemmal Ca2+ currents were measured in indo 1-loaded isolated rabbit ventricular myocytes during whole cell voltage clamp to quantitate the components of cytosolic Ca2+ influx and to describe the dynamic aspects of cytosolic Ca2+ buffering during steady-state contraction (0.5 Hz, 22 degrees C). Sarcolemmal Ca2+ influx was directly measured from the integrated Ca2+ current (I-Ca) recorded during the clamp (158 +/- 10 attomoles; amol). Sarcoplasmic reticulum (SR) Ca2+ content was determined from the integrated electrogenic Na+/Ca2+ exchange current (I-X) induced during rapid application and sustained exposure of cells to caffeine to elicit the release of the SR Ca2+ load (1,208 +/- 170 amol). The mean steady-state SR Ca2+ load was calculated to be 87 +/- 131 mu M (pmol/l nonmitochondrial cytosolic volume). Ca2+ influx via I-Ca represented similar to 14% of the stored SR Ca2+ and 23% of the total cytosolic Ca2+ flux during a twitch (47 +/- 6 mu M) Comparison of electrophysiologically measured Ca2+ fluxes with Ca2+ transients yields apparent buffering values of 60 for caffeine contractures and 110 for twitches (Delta Ca2+ total/Delta Ca2+ free). This is consistent with the occurrence of ''active'' buffering of cytosolic Ca2+ by SR Ca2+ uptake during the twitch.